In the case of a general automatic transmission system, because a torque converter functions as a fluid clutch, a damping effect may be achieved. This is advantageous when launching a vehicle or shifting between gears.
Meanwhile, an Automated Manual Transmission (AMT) system and a Dual-Clutch Transmission (DCT) system automatically control a clutch based on a manual transmission mechanism, and moreover do not use a torque converter, thus resulting in high fuel efficiency.
Here, the AMT system improves fuel efficiency and power transmission efficiency by directly connecting an engine to a clutch, but has no damping element. Accordingly, it is problematic in that a sudden shock, clutch slippage and the like may occur when torque changes. Therefore, there is a need for an algorithm for learning the touch point of the clutch in real time.
During such a learning process, when the learned touch point of a clutch (the position of an actuator when clutch torque is applied) is lowered below the actual position due to some unknown disturbance, the clutch cannot be engaged.
Here, if the stroke (position) of a clutch actuator can be moved within a mechanically permissible range, engine torque may be delivered, but because there is a limitation as to the amount of torque that the engine may output at idle speed during creep driving, an infinite increase in the clutch torque may result in engine hesitation.
In order to prevent this, the clutch torque during creep driving has an upper limit, and when the stroke of the clutch actuator is not continuously increased due to the upper limit, the clutch cannot be engaged, and thus a vehicle may be unable to start moving. In this case, it may be erroneously determined that the vehicle has developed an error.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.